Conventionally, as an exemplary cooling device for cooling a cooling target (target to be cooled) such as superconducting field poles of a superconducting rotary machine, for the purpose of, for example, keeping the cooling target in a superconductive state, a rotary machine having a cooling structure for cooling the cooling target with latent heat generated by evaporation of a liquid phase cooling medium, by a thermosiphon method and/or a heat pipe method, etc., is known. The following Patent Literature 1 discloses a rotary machine in which a cooling medium (liquid phase cooling medium) generated by condensation in a condenser cooled by a cooling device is delivered to a central hollow space formed inside a rotor of the rotary machine through a coupling pipe, and the liquid phase cooling medium is evaporated into a gas phase cooling medium in the central hollow space to cool windings (cooling target) wound around a winding holder provided to surround the central hollow space via the winding holder. In this rotary machine, the gas phase cooling medium generated by evaporation of the liquid phase cooling medium, inside the central hollow space, is returned to the condenser through the same coupling pipe, cooled and condensed again into the liquid phase cooling medium.